CocoaPods and build.sh updates

- Updated podspec to support both iOS & OSX
- `clean` now removes all non git-versioned files (except `core/`)
- added `browser` target
- added `deploy` target
- added `pod-deploy` target
Indeed, but the we should tell users to invoke build.sh with bash instead of sh. We don't know what features of `bash` will Apple remove from `sh` on future releases.